Image forming materials for transferring a photosensitive resin layer onto a substrate are known from, for example, JP-B-56-40824 (U.S. Pat. No. 3,884,693; the term "JP-B" as used herein means an "examined published Japanese patent application"). These types of image forming materials are used in the manufacture of printed circuit boards, intaglio or relief printing plates, name plates, multicolor printing proofs, offset printing plates, screen printing stencils, etc. The transfer material is composed of a temporary substrate, a separating layer, and a photopolymerizable layer, and image formation using the transfer material is carried out by adhering the photopolymerizable layer to a permanent substrate, stripping the temporary substrate off the transfer material, exposing the photopolymerizable layer to light via the separating layer, and developing the exposed photopolymerizable layer to form an image on the permanent substrate. The separating layer serves as an oxygen barrier so that the transfer material can be handled and exposed in an air atmosphere. Having a very small thickness of from about 0.5 to 5 .mu.m, the separating layer does not adversely affect the resolving power.
However, where the substrate to which a photopolymerizable layer is to be transferred has an uneven surface, it often happens that air bubbles are formed between the substrate and the very thin photopolymerizable layer, resulting in a failure of transfer.
JP-A-2-213849 (European Patent 373,438; the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a transfer material having an intermediate layer of a polyvinyl alcohol derivative, etc. between a temporary substrate and a photosensitive resin layer. Provision of the intermediate layer is directed to improving releasability of the temporary substrate and dissolving characteristics of the intermediate layer, with no consideration being given to transfer properties in the case where the transfer material is transferred to a permanent substrate having an uneven surface.
JP-A-63-309946 (U.S. Pat. Nos. 4,902,363 and 4,939,029) points out the occurrence of transfer failure due to insufficient adhesion of a transfer layer to a permanent substrate where the substrate has fine irregularities on its surface or where the substrate and/or the transfer layer have thereon fine particles such as refuse and dust. In order to prevent such adhesion failure, the publication teaches the use of a compressive temporary substrate. This means is certainly effective but is still insufficient for preventing of forming bubbles where a non-tacky photosensitive resin layer is transferred at room temperature to a substrate with a surface roughness equal to the thickness of the photosensitive resin layer.
Japanese Patent Application No. 120228/91 (corresponding to U.S. Pat. No. 5,292,613) discloses a transfer method using a photosensitive transfer material comprising a temporary substrate, particularly a gelatin-coated plastic film, having thereon a thermoplastic resin layer, a separating layer, and a photosensitive resin layer in this order, in which the photosensitive resin layer is adhered to a permanent substrate, and the temporary substrate and the thermoplastic resin layer are simultaneously stripped off to transfer the photosensitive resin layer onto the permanent substrate. According to this method, however, release between the thermoplastic resin layer and the separating layer is not always easily controlled, which is a disadvantage in automating the release operation.